Neither South Carolina nor the nation can afford four more years of President Obama, and Mitt Romney is the right person to take him on and get America back on track.

GREENVILLE, S.C. — Challenging Newt Gingrich's claim to South Carolina, Republican presidential candidate Mitt Romney charged into the state Friday with a key endorsement from the tea party-aligned governor, a packed campaign schedule and plans to start airing TV ads in the early primary state.

The show of force by Romney was a clear signal he intends to compete aggressively in a state that stymied him in 2008 and that Gingrich has made a cornerstone of his own campaign.

"It's a real kickoff of a major portion of our campaign," Romney told reporters after accepting an endorsement from South Carolina Gov. Nikki Haley. "I want to win in South Carolina."

While Romney was planting his flag in a Gingrich stronghold, the former House speaker from neighboring Georgia spent the day off the campaign trail, with a book-signing near Washington and private family events in the capital city.

On Friday and in the previous night's debate, Romney steered clear of pointed attacks on Gingrich, entering the final sprint to the Jan. 3 leadoff Iowa caucuses with an air of confidence after a week of assailing Gingrich's leadership, judgment and temperament. That pivot suggested the Romney camp believes Gingrich's recent rise in opinion polls may have leveled off and Romney can campaign closer to his early stance as the all-but-inevitable nominee.

The New Hampshire primary follows one week after Iowa, then comes South Carolina on Jan. 21. While Romney was still in Iowa on Friday, Haley announced she was supporting him as the best Republican candidate to take on President Barack Obama in the battle for the White House next year.

South Carolina wasn't kind to Romney in 2008. He spent millions here only to come in fourth after disappointing losses in Iowa and New Hampshire. Critics suggested his Mormon faith caused problems with the state's significant conservative Christian vote.

On Friday, Haley argued that her state was past all that. "South Carolina just elected a 38-year-old Indian female for governor," said Haley, who was raised Sikh and converted to Christianity. "What the people of South Carolina care about is values and family and faith."

Not that Friday was all smooth sailing for Romney.

After more than a week of criticizing Gingrich as a loose cannon likely to be savaged by Democrats, Romney opened himself to similar complaints by saying he didn't understand Medicaid until he started working in government. One of the principal avenues of criticism against Romney is that he's spent his life among the privileged and is out-of-touch.

"You know, I have to admit I didn't know all the differences between these things before I got into government," Romney said, referring to the federal-state health care program for the poor, at a campaign stop in Iowa.

Romney later told reporters traveling with him to South Carolina that he understood the program but hadn't quite grasped how it was funded. He called his earlier comment a "self-deprecating understatement."

Meanwhile, he had no harsh words for Gingrich — seeming content to leave that to his fellow Republican rivals and a political action committee that supports Romney. They have gone after Gingrich aggressively since he claimed the lead in national and Iowa polls this month.

The closest Romney came Friday was a veiled reference to the former congressional leader and longtime Washington consultant.

"What concerns me is that we have in Washington, D.C., a class of people who spent their whole time in Washington," Romney said.

His introductory South Carolina TV spot is upbeat.

The ad cost is modest, just $65,000 on cable television this week and next. But it signals an effort to cut into Gingrich's South Carolina showing heading into the bigger Florida primary, set for Jan. 31.

Romney was confident and relaxed campaigning Friday, traveling with his wife, Ann, and bringing reporters along on the campaign's charter flights for the first time this year.

Romney also hopes to slow Gingrich heading into New Hampshire, a must-win state for Romney, who was governor in next-door Massachusetts. Romney, who has led comfortably in New Hampshire, began airing a new ad there featuring his conversations with New Englanders concerned about the economy.

Romney already had set aside campaign money to step up his South Carolina effort, although the focus will probably remain on advertising, not additional campaign staff.

No doubt in the works for South Carolina is another Romney ad before the Jan. 21 primary, one featuring Haley.

Haley's ties with Romney run deep. She endorsed him in 2008 when she was in the Legislature. Romney returned the favor when she ran for governor in 2010.

"Neither South Carolina nor the nation can afford four more years of President Obama, and Mitt Romney is the right person to take him on and get America back on track," Haley, a rising GOP star, said after announcing her endorsement on Fox News Channel.

She later told The Associated Press that Romney "has led in making decisions," a point Romney stresses in suggesting his decades in business and term as governor qualify him most for the GOP nomination.

Romney has focused heavily on winning New Hampshire's primary on Jan. 10. But he has been spending time, too, in Iowa, where he finished a disappointing second to Arkansas' Mike Huckabee after spending $10 million on his 2008 Iowa campaign.

The candidates — except for Gingrich — were making final pitches to voters on Friday before people begin focusing on the holidays.

Bachmann and Texas Gov. Rick Perry were taking their argument that Gingrich isn't conservative enough to lead the party to Iowa voters on separate bus tours in the state's conservative but lightly populated northwest.

Although Gingrich was off the trail, his campaign drew unwanted attention after two New Hampshire Republicans alleged in complaints filed with state authorities that they had received illegal political telephone calls from the Gingrich operation.

New Hampshire law prevents political campaigns from using recorded political messages, or "robo-calls," to contact residents who are registered on a national do-not-call list.